1. Field of the Invention
The present invention relates to 3-substituted amino-5-pyrazolones and a process for producing the same. More particularly, the present invention is concerned with 3-substituted amino-5-pyrazolones containing at the 1-position a substituent containing at least one sulfo group and a process for producing the same.
2. Description of the Prior Art
The 3-substituted amino-5-pyrazolones containing a sulfo group or groups produced by the method of the present invention are important as magenta color formers (couplers) for silver halide color photographic light-sensitive materials, and, furthermore, as spectral sensitizers (for example, methine dyes) and dyes (for example, dyes for filters) for use in silver halide photographic light-sensitive elements.
The pyrazolones of the present invention are advantageous as compared to the corresponding 3-amino compounds in that since the absorption wavelength region thereof can be properly shifted into a longer wavelength region, color reproduction is improved, and, since the solubilities of the pyrazolones in the dye form in photographic processing solutions are high, contamination due to the dyes on a film or a photographic paper is low.
Although 3-amino-1-(4-sulfophenyl)-5-pyrazolones can be synthesized by reacting cyan acetic acid and p-sulfophenyl hydrazine by the method described in Organic Synthesis, Vol. 28, page 87 (1948), it is not possible to synthesize the corresponding 3-substituted amino compounds by this method. Several methods of producing 5-pyrazolones containing an anilino group as the substituted amino group at the 3-position are known. When these methods, however, disadvantages occur in that the processing steps are complicated, yields are low, or only pyrazolones with a specific structure can be used, and thus they are not applicable to the general production of 3-substituted amino-5-pyrazolones.
In the case of synthesizing pyrazolones containing a sulfo group or groups, the method of synthesizing 3-anilino-5-pyrazolones described in U.S. Pat. No. 2,343,703 cannot be used since, in accordance with this method, 3-amino-5-pyrazolone and aniline are condensed with the evolution of ammonia.
Also, the method of synthesizing 3-anilino-5-pyrazolones by the dehydration of pyrazolidine-3,5-dion and a substituted aniline as described in Japanese Patent Application (OPI) 92066/1974 cannot be used since the reaction does not proceed because of the low solubilities of reactants used.
British Pat. No. 1,007,847, in which a method of producing pyrazolones containing an acylamino, ureido or thioureido group as the substituent amino group is described, is directed to acylation, ureidation or thioureidation of 3-amino-5-pyrazolones and only discloses in detail the palmitoylation of 3-amino-5-pyrazolones containing a sulfo group in the potassium salt form. Thus, this method cannot be generally used as a method of synthesizing substituted amino-5-pyrazolones containing a sulfo group.
Organic compounds containing a sulfo group are often handled in the form of the alkali metal, alkaline earth metal or like salts throughout isolation or purification steps. Such alkali metal salts or alkaline earth metal salts are markedly water soluble, while their solubilities in organic solvents are markedly low. Thus they are suitable for use in reactions using aqueous systems, but not suitable for those using organic solvents. In effecting organic chemical reactions, an organic solvent system has advantages over an aqueous system in that various kinds of reactions can be carried out, and, furthermore, operations such as isolation, purification, etc., are easy.
Since the 3-substituted amino-5-pyrazolones containing a sulfo group can be handled in an organic solvent system, they can advantageously be subjected to various organic chemical reactions. There are various kinds of organic compounds containing a sulfo group which can be used as additives for photographic light-sensitive materials, and the production of these organic compounds can be carried out advantageously in an organic solvent system in the case that the sulfo group of the starting materials, i.e., the sulfo group-containing organic compound, e.g., a 3-substituted amino-5-pyrazolones, is in the form of a free acid or in the form of the ammonium or organic base (for instance, a primary, secondary or tertiary amine) salt thereof.